1. Field of the Invention
The present invention relates to an improved shake correcting apparatus for correcting shake, e.g., in a camera, by driving a correcting system using electromagnetic driving means which comprises a coil unit and a permanent magnet.
2. Description of the Related Art
In recent cameras, principal image pick-up operations such as exposure time determination and focusing have been entirely automated, so that even people inexperienced in camera operation can perform image pick-up with rare failure.
Also, a system for preventing shake applied to a camera has been recently developed, so that there is no factor inducing failure in image pick-up.
A system for preventing camera shake will now be simply described.
Camera-shake generally has frequencies of 1 to 10 Hz. A basic concept for enabling image pick-up while eliminating shake, even when such shake is produced at the time of shutter release, is that vibration due to camera-shake is detected and a correction lens displaced according to the detected value. Therefore, in order to take a photograph without image-shake, even when camera-shake is produced, it is required that vibration of a camera is first detected and then changes in an optical axis due to the camera-shake are corrected.
The vibration (camera-shake) is principally detected by attaching vibration detecting means to a camera for detecting linear acceleration, angular acceleration, angular velocity, angular displacement, and so forth, and for properly computing the output for camera-shake correction. Based on the detected information, image-shake control is performed by driving a camera-shake correcting apparatus that varies an image pick-up optical axis.
A conventional camera-shake correcting apparatus such as the apparatus disclosed in Japanese Patent Laid-Open No. 10-26779 comprises a supporting frame for supporting a lens or an image pick-up element, a correcting system having a permanent magnet fixed to the supporting frame for generating a magnetic field approximately parallel to an optical axis of the lens or the image pick-up element, and a supporting member for supporting the correcting system movably on a surface orthogonal to the optical axis and having a coil at a position opposing the permanent magnet for the purpose of reducing the size and weight of the apparatus.
In order to drive the supporting frame by such a shake correcting apparatus in a plane orthogonal to an optical axis of the lens or the image pick-up element, a permanent magnet (which is not a coil requiring connections for electric supply) is provided on a side of the correction system (the supporting frame side), so as to eliminate any requirement for supplying electricity to the correction system to drive it, and so as to dispense with any connection process required for electric supply.
FIGS. 12 and 13 illustrate a specific structure, in which yokes 505p and 505y having permanent magnets 503p and 503y respectively adhered thereon are fixed to a supporting frame 502 for supporting a correction lens 501 by crimping or screwing (permanent magnets 503p and 503y have complimentary structures in the pitch and yaw orientations, respectively; thus, for simplicity only the permanent magnet 503p is shown in FIG. 13). Coils 507p and 507y are attached on a surface of a bottom board 506 opposing the permanent magnets 503p and 503y (coils 507p and 507y have complimentary structures in the pitch and yaw orientations, respectively; thus, for simplicity only coil 507y is shown in FIG. 13).
In a shake correcting apparatus disclosed in Japanese Patent Laid-Open No. 10-26780, as shown in FIGS. 14A to 14C, a coil 507p (507y) having substantially the same structure as mentioned above is fixed to a bottom board (not shown) for supporting the correction lens with claws 509, etc., via a frame board 508 so as to simplify assembling.
In a shake correcting apparatus disclosed in Japanese Patent Laid-Open No. 11-212134, as shown in FIG. 15, a coil unit 606p having a coil 605 is pulled in and fixed to a bottom board 601 with a screw 604 inserted into a hole 603 from the bottom surface of the bottom board 601 as viewed in the drawing. In order to maintain high accuracy in an air gap, coil retainers 607 and 608 are formed on the bottom board 601, enabling the coil unit 606p to be positioned so that it is difficult to separate coil unit 606p from positioning projections 609. The coil retainers 607 and 608 also prevent the coil unit 606p from being warped and deflected when it is pulled in with the screw 604 so as to avoid interfering with permanent magnet 610p, etc. In addition, a substrate 602 is provided for mounting electrical components.
Also, in an actuator for a vibration proof apparatus disclosed in Japanese Patent Laid-Open No. 11-135597, as shown in FIG. 16, there are arranged a magnet 701, a coil 702 disposed so as to oppose the magnet 701 for supplying a driving force to the magnet 701 by electric charging, and a damper board 703 being a non-magnetic metallic plate and disposed between the magnet 701 and the coil 702, so that a damping effect is obtained by utilizing magnetic friction produced between the damper board 703 and the magnet 701. The coil 702 is fixed to the damper board 703, thereby facilitating control of an air gap between the magnet 701 and the coil 702; inserting the damper board 703 thus enables the structure to restrain any increase in the air gap as much as possible.
In a shake correcting apparatus as described above, stabilizing a driving force for correcting a shake is required; however, there has been a problem of large individual differences in the generated driving force from one apparatus to another apparatus because, when the thicknesses of the coil, which is liable to vary widely due to manufacturing error, and the coil unit formed of the coil are changed, the air gap between the permanent magnet and the coil, which has a large effect on the driving force for correcting the shake, is also changed.
As the air gap decreases, the driving force is increased; however, there has been a limit in the amount the air gap may be decreased while still avoiding contact between the coil and the permanent magnet due to a warp of the coil. For example, a structure disclosed in Japanese Patent Laid-Open No. 11-212134, shown in FIG. 15, is provided to improve accuracy in the air gap; however, since the coil unit 606p is pulled in and fixed to the bottom board 601 with the screw 604 inserted into the hole 603 from the bottom surface of the bottom board 601 as viewed in the drawing, an abutting face of the coil unit 606p is not a surface opposing the permanent magnet 610p, but an opposite surface thereto, so that when the thickness of the coil unit 606p varies, an air gap between the permanent magnet 610p and the coil 605 also varies. Although forming the coil retainers 607 and 608 on the bottom board 601 prevents the coil unit 606p from being warped and deflected when it is pulled in with the screw 604 so as to avoid interfering with a permanent magnet 610p, etc., since the position of the coil 605 is not always restricted by the coil retainers 607 and 608, variation in an air gap cannot be reliably prevented.
Also, in an actuator for a vibration proof apparatus disclosed in Japanese Patent Laid-Open No. 11-135597, as shown in FIG. 16, although fixing the coil 702 to the damper board 703 facilitates controlling the size of an air gap between the magnet 701 and the coil 702, since there is rarely a gap between a bottom board 704 and the coil 702, when the thickness of the coil 702 varies (e.g., becomes larger, as shown in FIG. 17), the air gap also varies. That is, fixing the coil 702 to the damper board 703, alone, cannot absorb variation in the thickness of the coil 702.
It is one object of the present invention to provide a shake correcting apparatus capable of reducing individual differences in a driving force for correcting shake due to manufacturing errors of the coil unit and the permanent magnet and to deformation in assembling.
It is another object of the present invention to provide a shake correcting apparatus capable of improving reliability in correcting a shake.
In one aspect, the present invention relates to a shake correcting apparatus comprising a bottom board, a supporting frame for supporting a shake correcting optical system, and an electromagnetic driving unit that drives the shake correcting optical system to perform shake correction. The electromagnetic driving unit comprises a coil unit attached to one of the bottom board and the supporting frame and a permanent magnet attached to the other one of the bottom board and the supporting frame, where the coil unit and permanent magnet have opposing surfaces. The shake correcting apparatus further comprises means for forming a space for absorbing a thickness variation of one of the coil unit and the permanent magnet on at least one of respective sides of the coil unit and the permanent magnet opposite the opposing surfaces of the coil unit and the permanent magnet.
In another aspect, the present invention relates to a shake correcting apparatus comprising a bottom board, a supporting frame for supporting a shake correcting optical system, and an electromagnetic driving unit that drives the shake correcting apparatus to perform shake correction. The electromagnetic driving unit comprises a coil attached to one of the bottom board and the supporting frame and a permanent magnet attached to the other one of the bottom board and the supporting frame, and the shake correcting apparatus further comprises a restricting member formed of a non-magnetic and conductive material that maintains constant a size of a gap between the coil and the permanent magnet.
In another aspect, the present invention relates to a shake correcting apparatus comprising a bottom board, a supporting frame for supporting a shake correcting optical system, and an electromagnetic driving unit that drives the supporting frame to perform shake correction. The electromagnetic driving unit comprises a coil attached to one of the bottom board and the supporting frame, and a permanent magnet attached to the other one of the supporting frame and the bottom board, and the shake correction apparatus further comprises an adjusting member for adjustably setting a gap between the coil and the permanent magnet.
In another aspect, the present invention relates to a shake correcting apparatus comprising a bottom board, a supporting frame for supporting a shake correcting optical system, and an electromagnetic driving device comprising a coil attached to one of the bottom board and the supporting frame and a permanent magnet attached to the other one of the bottom board and the supporting frame, where an electromagnetic driving force is generated between the coil and the permanent magnet by passing a current through the coil, and the supporting member is driven by the driving force on a plane orthogonal to an optical axis. The shake correcting apparatus further comprises a damper member attached to one of the bottom board and the supporting frame and further attached to one of opposing surfaces of the coil and the permanent magnet, where the damper member maintains the coil and the permanent magnet at a predetermined spacing.
In another aspect, the present invention relates to a shake correcting apparatus comprising a bottom board, a supporting frame for supporting a shake correcting optical system, and an electromagnetic driving device comprising a coil attached to one of the bottom board and the supporting frame and a permanent magnet attached to the other one of the bottom board and the supporting frame, where the electromagnetic driving device generates a driving force between the coil and the permanent magnet by passing a current through the coil, and the supporting member is driven by the driving force on a plane orthogonal to an optical axis. The shake correcting apparatus further comprises an adjusting member attached to one of the bottom board and the supporting frame, and further provided on one of opposing surfaces between the coil and the permanent magnet, where the thickness of the adjusting member is predetermined to set a size of a gap between the coil and the permanent magnet, and wherein the permanent magnet is opposed to the coil at a predetermined spacing.
Effects of the present invention are summarized as follows.
1) In a shake correcting apparatus in which a correcting system is electromagnetic driven by electromagnetic driving means comprising a coil unit and a permanent magnet so as to correct shake, a space for absorbing any thickness variation of the coil unit or the permanent magnet is arranged on at least one of two respective sides opposite the opposing surfaces between the coil unit and the permanent magnet, thereby reducing individual differences in the shake correction driving force from one apparatus to another apparatus due to manufacturing errors or deformation in assembling of the coil unit and the permanent magnet, etc.
2) At least one of the coil unit and the permanent magnet is supported relative to the bottom board or the supporting frame via an intermediate member, thereby reducing individual differences in the shake correction driving force from one apparatus to another apparatus due to manufacturing errors or deformation in assembling of the coil unit and the permanent magnet, etc.
3) The above-mentioned intermediate member is formed of a non-magnetic and conductive material so as to have a known damping effect, enabling the apparatus to be miniaturized, and improving reliability.
4) The coil (or the coil unit) held by the bottom board or the supporting frame is arranged so as to control the size of a gap between the permanent magnet and the coil by using the damper member, thereby reducing individual differences in the shake correction driving force from one apparatus to another apparatus due to manufacturing errors or deformation in assembling of the coil unit and the permanent magnet, etc., enabling the apparatus to be miniaturized, and improving reliability.
5) At least one of the coil (or the coil unit) and the permanent magnet is supported relative to the bottom board or the supporting frame via an adjusting member for adjusting the size of a gap between the coil and the permanent magnet, thereby reducing individual differences in the shake correction driving force from one apparatus to another apparatus due to manufacturing errors or deformation in assembling of the coil unit and the permanent magnet, etc.
6) The above-mentioned adjusting member is formed as a single unit with the yoke, enabling the apparatus to be miniaturized.
Further objects, features and advantages of the present invention will become apparent from the following description of the preferred embodiments with reference to the attached drawings.